An ice house keeps winter ice through the summer by doing three things at once: shading the stack, draining meltwater away at once, and surrounding the ice with thick dry insulation on every side. A bigger stack loses a smaller share of its ice, because the ice grows with the cube of its size while the surface that admits heat grows only with the square.
Part of Refrigeration
Harvesting lake or river ice in winter and storing it in an insulated, drained structure so it lasts into the warm season.
Mass, Insulation And Drainage Decide How Long The Ice Lasts
Ice stored in the open melts because the air, the ground and the sun all pump heat into it. Each design choice cuts one of those routes. The corpus covers the building in Cold Storage: Passive Cooling for Perishables and in Ice Cellar; this page keeps to the principles and the arithmetic.
- Shade and north slope. The carrier for this tree puts the pit on a shaded north-facing slope in the Northern Hemisphere, south-facing in the Southern.
- Drainage. Meltwater that pools warms the ice that sits in it and carries heat to the ice below. A gravel floor lets it escape.
- Insulation on every side. The corpus gives sawdust, straw, dead leaves or dried moss 300 to 600 mm thick between walls, and about 500 mm over the top once the house is full.
- No air gaps in the stack. Gaps let air circulate and carry heat through the pile. Pack blocks tight and fill the cracks with snow or ice chips.
- Open it as little as possible. Take ice through a small hatch, not by opening the whole structure.
The corpus reports that a well-built house in a temperate climate holds ice from January until August or September, and that sawdust and shade make it last two to three times as long as a house without them. The refrigeration carrier says 50 to 70% of the harvested ice survives to late summer in a well-insulated pit.
What You Need
- A saw and tongs for cutting and lifting blocks, as listed in the corpus cold-storage article.
- Dry insulation: sawdust, straw or dried moss, enough for the full thickness on all sides. Sawdust conducts about 0.058 W/m·K in the corpus table in Natural Insulation Materials; keep it dry, because damp insulation conducts far more.
- A drained site: gravel base and a slope for water to leave.
- Ice thick enough to cut safely. The corpus gives 200 to 300 mm for harvesting blocks in the cold-storage article and at least 15 cm in the refrigeration carrier, so treat the thickness as a local judgement and not a number to rely on.
Method: Fill The House Tightly, Then Leave It Alone
Step 1: Cut and lift blocks. Mark a grid on the ice, score the lines and saw through. The corpus gives the traditional block as 560 × 560 × 350 mm. Push cut blocks to a clear area of water, lift them with tongs and move them on an insulated sledge straight to the store.
Step 2: Lay a floor of insulation and gravel. Water must run away, and the ice must not sit on bare earth.
Step 3: Stack blocks tight in layers. Offset the joints. Fill every gap with snow or ice chips. Leave an insulation gap of at least the full wall thickness between the stack and the wall.
Step 4: Cover the whole stack with dry insulation before closing. When done right, the stack is invisible from outside, and the hatch is the only part you open.
Step 5: Draw ice from one point, in the same order, and close behind you. When it is going wrong, you find standing water, wet insulation or a warm draught at the hatch.
Worked Example: A Larger Stack Loses A Smaller Fraction Of Its Ice
Block weight. 0.56 × 0.56 × 0.35 = 0.110 m³. At an ice density of about 917 kg/m³ (a recalled figure, flagged), that is 0.110 × 917 = about 101 kg. The corpus says about 90 kg. Plan the lifting for the heavier figure.
Size effect, geometry only. A cube of side L has surface 6L² and volume L³, so surface per unit volume is 6 ÷ L.
- Side 1 m: 6 ÷ 1 = 6 m² of surface for each m³ of ice.
- Side 2 m: 6 ÷ 2 = 3 m² of surface for each m³ of ice.
Doubling the side halves the surface each cubic metre of ice has to defend, which is the carrier’s remark that mass is your ally.
Conduction floor for a 2 m cube. Inputs: sawdust k = 0.058 W/m·K, 0.5 m of it on all six faces, surface 6 × 2² = 24 m², and an assumed 20 K difference between outside air and ice.
- Heat flow: Q = k × A × ΔT ÷ L = 0.058 × 24 × 20 ÷ 0.5 = 55.7 W.
- Per day: 55.7 × 86,400 = 4.81 MJ.
- Ice melted per day: 4.81 MJ ÷ 334 kJ/kg = 14.4 kg, using the corpus 334 J/g.
- The stack holds 8 m³ × 917 = about 7.3 tonnes, so the loss is about 0.2% a day.
- Over an assumed 150 days: 14.4 × 150 = about 2.2 tonnes, roughly 30% of the stack.
This is a floor, not a forecast. It counts conduction through dry insulation only. Air gaps, a leaking hatch, damp sawdust and warm meltwater all add to it, which is how a real house loses more than the arithmetic suggests. The corpus figure of 50 to 70% surviving is the better planning number, and this calculation shows only why a small, poorly packed stack does worse.
Common Mistakes
- Letting meltwater pool. It carries heat through the pile and speeds the loss. Check the drain before the first block goes in.
- Skimping the roof. Heat comes down from the sun as well as in through the sides; the top layer is the one that gets forgotten.
- Opening the whole door to take one block. Each opening exchanges warm air for cold. Use the hatch.
- Storing insulation damp. Wet sawdust conducts heat far better than dry sawdust.
Safety
Ice work is drowning, crush and cut risk
Never cut ice alone or without a rope and a way to reach someone who falls in. A 100 kg block can crush a foot or a hand against a sledge or a wall, and saws and tongs are sharp. Do not climb into a deep pit while stacking; cold air and meltwater can sit in the bottom, and a fall into a pit with a stack of blocks injures. Keep dry insulation away from lamps, flues and sparks, because sawdust and straw burn.
What’s Next
- Learn next: Ice Making — producing ice when winter does not supply it
- Combine with: Insulation & Construction — the same insulation rules apply to a machine-cooled room